Animation: A Binary and Its Planets

This artist's movie illustrates Kepler-47, the first transiting circumbinary system -- a system with more than one planet orbiting a pair of stars -- 4,900 light-years from Earth, in the constellation Cygnus.. The system was detected by NASA's Kepler space telescope, which measures minisucule changes in the brightness of more than 150,000 stars to search for planets that pass in front of or 'transit' their host star. The movie begins by showing a birds-eye view of the system as it zooms in on the host stars. Swiping around behind the pair of the stars, the inner planet, Kepler-47c, comes into view. With an orbit of less than 50 days and about three times the radius of Earth, Kepler-47b is the smallest known transiting circumbinary planet. Continuing through the system to the outer planet, Kepler-47c has an orbital period of 303 days. This places it in the so-called "habitable zone," the region in a planetary system where liquid water might exist on the surface of a planet. While not a world hospitable for life, Kepler-47c is thought to be a gaseous giant, slightly larger than Neptune, where an atmosphere of thick bright water-vapor clouds might exist. From a distance, both Kepler-47c Kepler-47b are shown transiting their host pair as the two stars eclipse one another every 7.5 days. The larger G-type star is similar to the sun in size, but only 84 percent as bright. The second M-type star is diminutive, measuring only one-third the size of the sun and less than one percent as bright. In less than a year since the announcement of the first circumbinary planet, Kepler-16b, this discovery proves that more than one planet can form and persist in the stressful realm of a binary star. The discovery demonstrates the diversity of planetary systems in our galaxy and provides more opportunities to search for life as we know it. Credit: NASA/JPL-Caltech/T. Pyle